The invention relates to an insulating plate consisting of expanded aminoplastic resinous material having a reinforcement of mineral fibers embedded therein.
It is known to prepare insulating plates having poor heat conductivity and good sound-absorbing properties on the basis of different expanded and foamed plastics, including aminoplastic resinous materials. Although the known aminoplastic foams have several advantageous properties, such as odorlessness and a favorable behavior against the action of flames, they are relatively brittle and have low mechanical strength. It has been attempted also to improve the mechanical properties of thermoplastic foams by embedding reinforcing fibers, and for that purpose short fibers or chips of fibrous material have been admixed to the mass of synthetic resin to be expanded. However, this complicates the operation for preparing insulating plates and bodies, increases the expenditure of material and the specific weight of the insulating bodies, and normally results in only a moderate improvement of the mechanical properties. Furthermore, in the preparation of insulating plates, flat fibrous structures have been inserted, especially fabrics, into the mass of synthetic resin to be foamed. However, also such a procedure does not provide a satisfactory improvement of the mechanical properties of such insulating bodies and plates, as frequently the bond or linkage of such inserts to the foam of the resinous material is not reliable and the placement of such an insert in the interior of a plate does not improve the mechanical properties in the surface region, whereas the provision of reinforcements at the surface eliminates positive properties of the foam structure.